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Chapter 4
Environmental Consequences
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Introduction

The National Environmental Policy Act (NEPA) requires that environmental assessments disclose the environmental impacts of a proposed federal action, reasonable alternatives to that action, and any adverse environmental effects that cannot be avoided if the proposed action is implemented. This chapter presents analyses of potential environmental impacts on natural, cultural, and social resources. The analyses provide the basis for comparing the effects of the three alternatives described in Chapter 2.

Methodologies

The methodologies used to conduct the environmental impact analyses are presented in this section. Methodologies are provided for project impacts as well as for cumulative impacts and impairment to park resources. Methodologies and assumptions common to all resource topic areas are presented first, followed by methodologies specific to individual resource topic areas.

Each resource topic includes a discussion of the project impacts and the duration, intensity, and type of each impact. These impact criteria are defined below.

• Duration – whether the impact would occur in the short term (temporary) or the long term (permanent).
  
• Intensity – whether the impact would be negligible, minor, moderate, or major.
  
• Type – whether the impact would be beneficial or adverse to the natural, cultural, or social environment.

Impacts are also considered in the context of whether they would be limited to the local setting or regional setting (see Chapter 3). In this analysis, local setting impacts would be those that occur within the Lower Yosemite Fall area. Regional impacts (i.e., those that would occur within Yosemite Valley), when viewed in combination with direct impacts of this project, are considered cumulative impacts.

The National Park Service is committed to the protection of wetlands. The wetland protection statutes that guide the National Park Service include Executive Order 11990, Protection of Wetlands; Director’s Order #77-1 (see Appendix A for further discussion), Wetland Protection, and its accompanying Procedural Manual #77-1; Clean Water Act Section 404; and the "no net loss" goal outlined by the White House Office on Environmental Policy in 1993. Executive Order 11990 requires that leadership be provided by involved agencies to minimize the destruction, loss, or degradation of wetlands. The National Park Service’s Director’s Order #77-1 and Procedural Manual #77-1 provide specific procedures for carrying out the Executive Order.

Wetlands in the Lower Yosemite Fall area were delineated and mapped in the field during the spring of 2001 to two standards: Cowardin wetlands and jurisdictional wetlands. Cowardin wetlands are used as the basis for analysis under National Park Service Wetland Protection Guidelines. Jurisdictional wetlands are used as a basis for analysis under Section 404 of the Clean Water Act. Wetland data were compared to each alternative to determine the area that would potentially be effected by the proposed project alternative. For wetlands, the area of potential effect is areas identified as having Cowardin and jurisdictional wetlands.

Duration of Impact. A short-term impact is defined as lasting less than 20 years following the implementation of an alternative. A long-term impact is defined as lasting longer than 20 years after implementation of an alternative.

Intensity of Impact. Three primary measures were used to evaluate the intensity of impacts on wetlands: the size and type of the wetland, the integrity of the wetland, and the connectivity of the wetland to adjacent habitats. The greater the size of a wetland and the strength of its linkages with neighboring ecological communities, the more valuable a wetland is for the integrity and maintenance of biotic and abiotic processes. The intensity of impacts has been described as negligible, minor, moderate, or major. Negligible impacts would be imperceptible or not detectable. Minor impacts would be slightly detectable, localized within a small area, and would not affect the overall viability of wetlands in the park. Moderate impacts would be apparent and have the potential to become major impacts. Major impacts would be substantial, highly noticeable, and could be permanent.

Type of Impact. Adverse impacts are those that would degrade the size, integrity, or connectivity of wetlands. Conversely, beneficial impacts would enlarge or enhance the size, integrity, and connectivity of wetlands.

The impact analysis for geology, geologic hazards, and soils focused on effects that geologic processes in Yosemite National Park would have on visitors, personnel, and facilities under each project alternative. Geologic processes can negatively affect visitors, personnel, and facilities when events such as rockfalls, earthquakes, and severe soil instability result in injury, death, or damage to facilities. The assessment also focused on effects the project alternatives would have on geologic processes—specifically, the formation and conservation of soil resources. Actions prescribed for the Lower Yosemite Fall Project could affect soil resources through accelerated erosion, soil loss, or soil removal.

Geologic risks that affect public safety are rarely predictable, and the extent to which they may affect people and property cannot be quantified. Analysis of effects was qualitative, and professional judgment has been applied to reach reasonable conclusions as to the context, duration, intensity, and type of potential impacts (see the Yosemite Valley Geologic Hazard Guideline in Appendix C of the Final Yosemite Valley Plan/SEIS).

Duration of Impact. Rockfall hazards would likely be long-term and permanent. The potential for rockfall is ongoing, as this natural process continues to occur in Yosemite Valley. Short-term impacts on soils would be those that could be restored when project construction is completed and are considered as those lasting 20 years or less. Long-term impacts would be considered as those lasting over 20 years.

Intensity of Impact. The intensity of an impact was based on its location within the Valley. The intensity of the impact would be negligible if facilities of any kind are located outside geologic hazard zones. The intensity of the impact would be considered a minor risk if standard occupancy and miscellaneous facilities are within the rockfall shadow zone. The intensity of the impact would be moderate if essential, hazardous, and special occupancy facilities are within the rockfall shadow zone, or standard occupancy and miscellaneous facilities are within the talus slope zone. The intensity of the impact would be considered major if essential, hazardous, and special occupancy facilities are within the talus slope zone. For soils, impact intensities are related to soil type, history of disturbance, and scale of measurability.

Type of Impact. All rockfall events are potentially hazardous. The type of impact is related to risk, and it is difficult to estimate risk involving natural events. In general, reducing risk is considered a beneficial impact. The type of impact would be considered beneficial if there would be a decrease in both the density of individuals and facilities from the talus slope zone; this includes moving them into the rockfall shadow zone, a zone of lower risk. It would also be considered beneficial if there would be a decrease in both the density of individuals and facilities from the rockfall shadow zone. Beneficial impacts to soils would be those that contribute to protecting or restoring natural soil conditions, including abiotic and biotic components, soils structure, and moisture. Adverse impacts would result in degradation of chemical, physical, abiotic, or biotic soil components.

Generally, maintaining facilities within or moving facilities into a zone of higher risk or exposing people to greater levels of risk was considered adverse. Specifically, the type of impact would be considered adverse if (1) essential and hazardous occupancy facilities remain in or are placed in the talus slope and rockfall shadow zones; or (2) special occupancy facilities remain or are placed in the talus slope zone.

This analysis focused on how the action alternatives (Alternatives 2 and 3), relative to the No Action Alternative, would affect hydrologic processes during project construction and operation. The hydrology impact assessment evaluates how construction activities, particularly on trails and bridges, would affect channel morphology, flooding, and water quality. Hydrology impacts were evaluated in terms of their context, duration, and intensity, and whether the impacts were considered to be beneficial or adverse.

The analysis examined potential changes to channel morphology (channel depth, position, and streamflow) as a result of actions in the alternatives. The analysis identified potential effects on water quality associated with construction operations, such as the location of construction staging areas near the braided stream channel and use of heavy equipment during construction.

Duration of Impact. Short-term impacts occur during the alternative’s implementation and are usually less than 2 years in duration (e.g., construction projects). Long-term impacts remain after the alternative has been implemented and are usually longer than 2 years in duration. Since the full implementation of an alternative would take place over a number of years, this section frequently assesses the duration of individual actions of the alternative (e.g., removal of a bridge) instead of full implementation of the alternative.

Intensity of Impact. Negligible impacts would be imperceptible or not detectable. Minor impacts would be slightly perceptible and localized, without the potential to expand if left alone. Moderate impacts would be apparent and have the potential to become larger. Major impacts would be substantial, highly noticeable, and may be permanent.

Type of Impact. Adverse impacts alter natural hydrologic conditions (e.g., impede flood flows, cause unnatural erosion or deposition, etc.) or degrade water quality (e.g., increase pollution or bacteria levels from recreational use). Beneficial impacts are those that restore natural hydrologic conditions (e.g., remove impediments to flood flows, stabilize riverbanks, etc.) or improve water quality (e.g., reduce non-point source pollution).

The analysis qualitatively analyzed the health and safety impacts to persons as well as potential property damage that would be caused by minor changes in the floodplain of the Merced River and its tributaries, as well as structures within the floodplain. The source of these minor changes includes the following: trail alignments, bridge rehabilitation and construction, restroom demolition and construction, and replacement of the parking area with either a seating area or a picnic area.

Duration of Impact. Short-term impacts (e.g., construction) would be those that occur over a period of less than 1 year. Long-term impacts would be those occurring for more than 1 year. All the impacts evaluated would be considered long term. The risk posed to construction personnel working in the floodplain (short term) was considered too small to warrant evaluation.

Intensity of Impact. Beneficial and adverse impacts of individual actions in each alternative were assigned intensities as they relate to effects on life/safety and property in the floodplain.

Definitions of impact intensities are provided in table 4-1.

Type of Impact. In the context of evaluating impacts of each alternative by evaluating risk to human life and property, removing structures from the 100-year floodplain was considered a beneficial impact to human life or property. Development of new Class I or Class II actions (non-exempted facilities) in the 100-year floodplain was considered an adverse impact to human life or property.

Two primary parameters were used to evaluate the intensity of impacts on vegetation: (1) the size and continuity of the plant community, and (2) the natural structure, productivity, diversity (integrity), and rarity of the plant community.

Other not-so-visible impacts (such as encroachment of wetland habitats by non-native species) would continue to be managed by the National Park Service in conjunction with National Park Service programs involved in the protection and long-term management of the park’s vegetative resources.

Duration of Impact. Long-term impacts have been defined as those that can be detected for longer than 20 years. Short-term impacts have been defined as those lasting less than 20 years.

Intensity of Impact. Negligible impacts would have no measurable or perceptible changes in plant community size, integrity, or continuity. Minor impacts would be measurable or perceptible and localized within a relatively small area. This means the overall viability of the plant community would not be affected. Moderate impacts would cause a change in the plant community (e.g., size, integrity, and continuity); however, the impact would remain localized. The change would be measurable and perceptible, but could be reversed. Major impacts would be substantial, highly noticeable, and could be permanent in their effect on plant community size, integrity, continuity, productivity, and structure.

Type of Impact. Impacts were classified as adverse if they would reduce the size, continuity, or integrity of a plant community. Conversely, impacts were classified as beneficial if they would increase the size, continuity, or integrity of a plant community.

The effects that the alternatives would have on wildlife and their habitat are addressed by considering the effects of alternatives on wildlife habitat as represented by general vegetation types. A description of how vegetation impacts would affect wildlife is provided.

Impacts on wildlife have been assessed in terms of changes in the amount and distribution of wildlife habitat, the size and connectivity of habitat, the integrity of the site (including past disturbance), the potential for habituation of wildlife to humans, and the relative importance of habitats.

Duration of Impact. Long-term impacts are defined as those lasting 20 years or longer. Short-term impacts would be expected to last for less than 20 years. All short-term impacts to wildlife and habitat from implementation of an alternative would relate to construction activities and their immediate effects on wildlife. These impacts would end with cessation of construction activity, or soon thereafter, and include the following:

• Noise, dust, and light emanating from construction sites could affect the use of surrounding habitats by wildlife.
  
• Vegetation removed, trampled, or run-over during temporary use of some habitat as areas for staging of machinery or materials would affect wildlife until such areas could be restored after the project.
  
• Diversion of water flows during construction would result in unnatural drying or wetting of habitats adjacent to sites.
  
• Wildlife could be injured or killed by traffic or machinery associated with construction.
  
• Pits and trenches could entrap wildlife, resulting in their death. Spills of fuel, oil, hydraulic fluid, antifreeze, and other toxic chemicals could affect wildlife, especially those in aquatic environments.
  
• Construction personnel, at in-park residences or at work sites, could provide human food to wildlife, resulting in conditioning of wildlife and human/wildlife conflicts.

Subsequent impact analyses focused primarily on long-term effects of implementation of the alternatives.

Intensity of Impact. Negligible impacts are impacts that would not be measurable or perceptible. Minor impacts would be measurable or perceptible and would be localized within a relatively small area; however, the overall viability of the resource would not be affected. Without further impacts, negative effects would be reversed, and the resource would recover. Moderate impacts would be sufficient to cause a change in the resource (e.g., abundance, distribution, quantity, or quality); however, the impact would remain localized. The change would be measurable and perceptible, but negative effects could be reversed. Major impacts would be substantial, highly noticeable, and could be permanent.

Type of Impact. Impacts were classified as adverse if they would negatively affect the size, continuity, or integrity of wildlife habitat. Conversely, impacts were classified as beneficial if they would positively affect the size, continuity, or integrity of wildlife habitat.

The National Park Service compiled a list of potential special-status species with potential habitat in the Lower Yosemite Fall area from three main sources: (1) a list of federal endangered and threatened species that may be affected, provided by the U.S. Fish and Wildlife Service, (2) species listed under the California Endangered Species Act or considered rare or sensitive by the California Department of Fish and Game, and (3) park rare plant species identified by the National Park Service. Almost 60 special-status species on this compiled list were evaluated for presence or potential habitat within the Lower Yosemite Fall area (see Appendix B). All species except bald eagle, American peregrine falcon, Wawona riffle beetle, harlequin duck, and special-status bats were found to be absent in the Lower Yosemite Fall area, and are not subject to further analysis in this chapter.

The impact evaluation for special-status wildlife species for each alternative was based on the following: (1) the possibility of a species or its preferred habitat types occurring in areas that may be affected, (2) the direct loss of habitat or individuals, (3) the partial loss of habitat from its modification, and (4) the species’ sensitivity to disturbance from human activities that may cause it to abandon currently occupied habitat or deter it from occupying suitable habitat.

Impacts have been evaluated considering species’ sensitivity to impacts (based on rarity, resilience, size of population, and extent of species throughout the park); location of species in proximity to new disturbance; and mitigation measures applied as appropriate for the species and the site.

Duration of Impact. The expected duration of impacts is described as long-term or short-term. Long-term impacts are defined as those that would last 20 years or longer, and short-term impacts are those that would last less than 20 years.

Intensity of Impact. The intensity and magnitude of impacts on special-status vegetation and wildlife species are described as negligible, minor, moderate, or major. Negligible impacts would be imperceptible or not detectable. Minor impacts would be slightly detectable, localized within a relatively small area, and not affect the overall viability of resources in the park; without further impacts, adverse effects would be reversed, and the resource would recover. Moderate impacts would be sufficient to cause a change in the resource (e.g., abundance, distribution, quantity, or quality), but would remain localized; they would be readily apparent. Major impacts would be substantial, highly noticeable, and affect larger areas.

Type of Impact. Impacts were classified as adverse if they would negatively affect individuals of federally listed species or the species population size, or habitat size, continuity, or integrity. Conversely, impacts were classified as beneficial if they would positively affect individuals of federally listed species or species population size, or the size, continuity, or integrity of habitat.

The air quality impact assessment evaluates how construction activities would affect air pollutant emissions and concentrations. Air quality impacts were evaluated in terms of their duration, intensity, and type, and whether the impacts were considered to be beneficial or adverse.

The air quality impact assessment involved the identification and qualitative description of the types of activities associated with the Lower Yosemite Fall Project that could affect air quality. A qualitative assessment was performed to evaluate the potential for higher pollutant emissions or concentrations, taking into account the frequency, magnitude, duration, location, and reversibility of the potential impact. In addition, regional pollutant sources and transport issues were evaluated in the context of regional cumulative impacts.

Duration of Impact. For this analysis, short-term impacts would be associated with construction and demolition activities that are temporary in nature, while vehicle emissions were quantified for a 15-year (2000-2015) time period and assumed to continue beyond 2015.

Intensity of Impact. The intensity of an impact was assessed based on whether the impact is judged to be negligible, minor, moderate, or major relative to Alternative 1. For this analysis, impacts that would increase or decrease air emissions or pollutant concentrations by 5% or less would be negligible; by 5% to 20% would be minor; by 21% to 50% would be moderate; by more than 50% would be major.

Type of Impact. Impacts were considered to be beneficial or adverse to air quality. Beneficial air quality impacts would reduce emissions or lower pollutant concentrations, while adverse impacts would increase emissions or raise pollutant concentrations.

The noise impact assessment involved the identification and description of the types of actions that could affect the ambient noise environment, corresponding noise sources, relative source strengths, and other characteristics. Based on the relative source strengths, a qualitative assessment was performed to evaluate the potential for a substantial increase in ambient noise levels. Assessments were also performed where noise-sensitive uses are located or would expose persons to excessive noise levels, taking into account the frequency, magnitude, duration, location, and reversibility of the potential impact.

Duration of Impact. Long-term impacts have a permanent effect on the ambient noise environment (visitor and operational activity). Short-term impacts are temporary in duration and would be associated with transitional types of impacts (construction activity is usually a short-term impact).

Intensity of Impact. Negligible impacts would not be detectable. Minor impacts would be slightly detectable in proximity to the source, but would not be expected to have an appreciable effect on ambient noise levels. Moderate impacts would be clearly detectable and could have an appreciable effect on ambient noise levels; moderate adverse impacts may include introduction of noise associated with an activity or facility into an area with little or no ambient noise. Major impacts would be clearly audible against ambient noise levels, or would have a substantial, highly noticeable effect on ambient noise levels.

Type of Impact. Beneficial impacts are those impacts that would result in less noise, and adverse impacts are those impacts that would result in more noise.

This impact analysis methodology applies to three basic types of cultural resources: archeological sites, ethnographic resources, and cultural landscape resources (including individually significant historic structures).

Cultural resource impacts in this document are described in terminology consistent with the regulations of the Council on Environmental Quality, and in compliance with the requirements of both the National Environmental Policy Act and Section 106 of the National Historic Preservation Act.

The National Historic Preservation Act requires determinations of no effect or effect, and where there would be an effect, a determination as to whether that effect would be adverse or not adverse. Archeological resources are typically considered eligible for inclusion in the National Register of Historic Places because of the information they have or may be likely to yield. Intensity of impacts to archeological resources relates to the importance of the information they contain and the extent of disturbance or degradation.

Council on Environmental Quality regulations call for a discussion of the "appropriateness" of mitigation, and Director’s Order 12 (Conservation Planning, Environmental Impact Analysis and Decision-Making; see Appendix A for further discussion) requires an analysis of the "effect" of mitigation. The reduction in intensity that would result from mitigation is an estimate of the effectiveness of mitigation under NEPA. It does not suggest that the level of effect as determined by Section 106 would be similarly reduced. Although adverse effects under Section 106 may be mitigated, the effect would remain adverse.

Mitigation for NEPA purposes in this environmental assessment is based on the park’s 1999 Programmatic Agreement and includes avoidance of adverse effects or application of one or more standard mitigation measures, described in stipulation VIII(A) of this agreement. According to stipulation VII(C) of the 1999 Programmatic Agreement, impacts to archeological resources are considered not adverse for purposes of Section 106 of the National Historic Preservation Act if data recovery is carried out in accordance with the 1999 research design. Under the revised regulations of the Advisory Council on Historic Preservation of May 18, 1999 (36 Code of Federal Regulations [CFR] 800, Protection of Historic Properties, Final Rule and Notice), data recovery is considered to be an adverse effect. However, according to Part 800.3(A)(2) of those revised regulations, provisions of programmatic agreements in existence at the effective date of the new regulations remain in effect. Therefore, archeological data recovery excavations are not considered adverse effects.

Section 106 Summary. Under regulations of the Advisory Council on Historic Preservation (36 CFR 800.9) addressing the criteria of effect and adverse effect, actions proposed under the action alternatives would have the potential to adversely affect significant historic properties. Ethnographic resources would be disturbed or destroyed by construction occurring in traditional plant-gathering areas, historic village sites, and/or places holding special sacred and spiritual significance to American Indians. Historic sites, structures, districts, and cultural landscape features would also be adversely affected by undertakings entailing substantial facility alteration or removal, or the introduction of modern non-contributing development within or in proximity to historic districts and sensitive landscape areas. To mitigate adverse effects, the park would utilize compatible design principles, carry out Historic Architectural Building Survey/Historic Architectural and Engineering Record documentation, salvage historic materials, develop cooperative agreement provisions for traditional plant gathering, or other suitable mitigation in accordance with the Programmatic Agreement.

Many archeological resources having varied potential to yield prehistoric and historic information would be affected by ground-disturbing activities. To avoid adverse effects to archeological resources, the park would carry out data recovery to retrieve important information, in accordance with the Programmatic Agreement.

The restoration of vegetation contributing to historic settings and the cultural landscape, and the removal of non-contributing structures and landscape elements also would have no adverse effect on historic properties. Rehabilitation would be carried out in accordance with the Secretary of the Interior’s Standards and Guidelines for Archeology and Historic Preservation (USDOI 1983).

For project areas lacking sufficient cultural resource data or design information to adequately assess effects, the park would carry out inventories, evaluate identified resources for national register significance, consult according to the stipulations of the Programmatic Agreement, and recommend avoidance or appropriate treatment/standard mitigation measures prior to construction disturbance.

Duration of Impact. Impacts to archeological resources could be of short-term, long-term, or permanent duration.

Type of Impact. Any change in the physical attributes of an archeological site is irreparable and considered adverse and of permanent duration. Adverse impacts to archeological resources most often occur as a result of earthmoving activities within an archeological site area, soil compaction or increased erosion, unauthorized surface collection, or vandalism. Beneficial impacts to archeological resources can occur when patterns of visitor use or management action are changed in the vicinity of archeological resources such that an ongoing impact, which would otherwise continue to degrade archeological resources, is reduced or arrested.

Intensity of Impact. The intensity of impact to an archeological resource would depend upon the potential of the resource to yield important information, as well as the extent of the physical disturbance or degradation. For example, major earthmoving at an archeological site with low data potential might result in a minor, adverse impact. Negligible impacts would be barely perceptible and not measurable, and would usually be confined to archeological sites with low data potential. Minor impacts would be perceptible and measurable, and would remain localized and confined to archeological site(s) with low to moderate data potential. Moderate impacts would be sufficient to cause a noticeable change, and would generally involve one or more archeological sites with moderate to high data potential. Major impacts would result in substantial and highly noticeable changes, involving archeological site(s) with high data potential.

Duration of Impact. Impacts are considered short term if they represent a temporary change in important vegetation or temporarily restrict access to an important resource, and do not disrupt the cultural traditions associated with that resource for a noticeable period of time. They are considered long term if they involve a change in important vegetation or cultural feature, or addition of a new facility or visitor use that would change the physical character of or access to a resource for a noticeable period of time. This period of time would vary by resource type and traditional practitioners. These long-term changes would disrupt cultural tradition(s) associated with the affected resource, but the disruption would not alter traditional activities to the extent that the important cultural traditions associated with the resource are lost. Permanent impacts to ethnographic resources would involve irreversible changes in important resources such that the ongoing cultural traditions associated with those resources are lost.

Type of Impact. Impacts to ethnographic resources occur as a result of changes in the physical characteristics, access to, or use of resources, such that the cultural traditions associated with those resources are changed or lost. Beneficial impacts can occur when intrusive facilities, or visitor or management activities are removed from a traditional use area; when ecological conditions are improved at a gathering area such that the traditionally used resource is enhanced; or when access for American Indian people is enhanced. Adverse impacts occur when physical changes to a traditionally used resource or its setting degrade the resource itself, or degrade access to or use of a resource.

Intensity of Impact. The intensity of impacts to an ethnographic resource would depend on the importance of the resource to an ongoing cultural tradition, as well as the extent of physical damage or change. Negligible impacts would be barely perceptible and not measurable, and would be confined to a small area or single contributing element of a larger National Register district (such as the ethnographic landscape in Yosemite Valley). Minor impacts would be perceptible and measurable, and would remain localized and confined to a single contributing element of a larger National Register district. Moderate impacts would be sufficient to cause a change in a significant characteristic of a National Register district or property, and/or would generally involve a small group of contributing elements in a larger National Register district. Major impacts would result in substantial and highly noticeable changes in significant characteristics of a National Register district or property, and/or would involve a large group of contributing elements in a larger National Register district and/or an individually significant property.

Duration of Impact. Impacts to cultural landscape resources are considered short term if they involve activities such as temporary removal of vegetation or other contributing resources, road closures, or prescribed burns, where the impacts are noticeable for a period of from 1 to 5 years. Other examples of short-term impacts to historic structures include constructing scaffolding surrounding a building during rehabilitation work, or minor deterioration in historic fabric that is repairable as part of routine maintenance and upkeep. Impacts are considered long term if they involve a reversible change, lasting from 5 to 20 years, in a significant characteristic of a historic structure or landscape. Permanent impacts to a historic structure or landscape resources would include irreversible changes in significant characteristics, such as removal of contributing resources; restoration of natural systems and features; irreversible removal of historic fabric that changes the historic character of a property; or demolition of a historic structure.

Type of Impact. Impacts to cultural landscape resources result from physical changes to significant characteristics of a resource or its setting. Beneficial impacts can occur as a result of restoration or rehabilitation of resources, or removal of incompatible or noncontributing facilities. Adverse impacts generally occur as a result of modifying a significant characteristic of a historic structure or landscape resource; removal of a significant structure or landscape resource; or addition of new, incompatible facilities in proximity to a historic site or structure.

Intensity of Impact. Negligible impacts would be barely perceptible and not measurable and would be confined to small areas or a single contributing element of a larger National Register district. Minor impacts would be perceptible and measurable but remain localized and confined to a single contributing element of a larger National Register district. Moderate impacts would be sufficient to cause a change in a significant characteristic of an individually significant historic structure, or would generally involve a single or small group of contributing elements in a larger National Register district. Major impacts would result from substantial and highly noticeable changes in significant characteristics of an individually significant historic structure, or would involve a large group of contributing elements in a National Register district.

The overriding management purpose of any national park, as defined by the National Park Service 1916 Organic Act, is to conserve the scenery and natural and historic objects. Following this direction, the National Park Service evaluated impacts on scenic resources by examining the potential effects of the Lower Yosemite Fall Project on the landscape character and/or features.

Impacts of the Lower Yosemite Fall Project on visual resources were examined and assessed by comparing the existing visual character of the landscape components and features and the degree to which actions that may result from the Lower Yosemite Fall Project would affect (i.e., contrast or conform with) these components and features.

Potential impacts to scenic resources consist of substantial changes that would alter (1) existing landscape character, whether foreground, intermediate ground, or background, and would be visible from viewing areas the National Park Service has established as important or (2) access to historically important viewing areas.

Duration of Impact. The duration of the impacts considers whether the impact would be short-term or long-term. A short-term impact would be short-lived or temporary due to construction, restoration, or demolition activities, and a long-term impact would be permanent and continual.

Intensity of Impact. The magnitude of impacts to the scenery within the view from specific vantage points and to specific scenic features is described as negligible, minor, moderate, or major depending upon their comparison to scenic categories presented in table 3-14 of the Yosemite Valley Plan (Vol. Ia, Chapter 3, page 3-69), and as described below.

• Negligible impacts would be imperceptible or not detectable.
  
• For the A Scenic category, minor impacts would be slightly detectable or localized within a relatively small area. For the B Scenic category, minor impacts would be slightly detectable, localized within a relatively small area, or readily apparent.
  
• For the A Scenic category, moderate impacts would be those that are readily apparent. For the B Scenic category, moderate impacts would be substantial, highly noticeable, and/or result in changing the character of the landscape.
  
• For the A Scenic category, major impacts would be substantial, highly noticeable, and/or result in changing the character of the landscape. For the B Scenic category, major impacts would be substantial, highly noticeable, and/or result in changing the character of the landscape by adding human-made features to a mostly undisturbed area or by removing most human-made features from a developed area.

Analysis of impacts to the Merced Wild and Scenic River’s scenic Outstandingly Remarkable Values can be found in Chapter 5 of this environmental assessment.

Type of Impact. All actions proposed in each alternative were analyzed using a geographic information system to evaluate the net change in each of the scenic categories (A, B, and C). This approach assesses the acreage of scenic categories A, B, and C that would be improved by the removal of development and restoration to natural communities, or affected by new development. Impacts were considered beneficial if they would decrease the number of acres disturbed within A and B Scenic resource categories, and considered adverse if actions within each alternative would increase the number of human-caused visual intrusions in these categories. Impacts were also considered beneficial if the quality of the visual experience would be improved, and adverse if the visual quality would be degraded. No C Scenic resources would be altered by any of the alternatives.

Impacts on visitor experience may occur as a result of changes to road circulation, interpretation facilities, trails, and other facilities and resources that contribute to the type and quality of the visit to Yosemite National Park. Impacts may also occur from direct actions, thereby altering the availability of a specific experience or activity.

Visitor experience is also directly affected by actions influencing natural resources such as air quality, scenic resources, and cultural resources. Though impacts to these resources are not repeated in the analysis of visitor experience, enhancement or degradation of these resources also enhances or degrades the quality of the visitor experience.

Impacts on visitor experience have been assessed using professional judgment to develop a qualitative analysis of the effects of actions to the Lower Yosemite Fall area. These conclusions have been considered in combination with data on the proportion, when known, of visitors who participate in different activities while in the park. Anticipated changes in visitor participation would represent an effect.

Duration of Impact. A short-term impact on visitor experiences would be temporary in duration because construction, restoration, or demolition activities would be temporary. A long-term impact would have a permanent effect on the visitor experience.

Intensity of Impact. The intensity of impacts are defined as negligible, minor, moderate, and major. Negligible impacts would result in little noticeable change in visitor experience. Minor impacts would result in changes in desired experiences but without appreciably limiting or enhancing critical characteristics. (Critical characteristics are those elements of a recreational activity that are most important to those who pursue it; for example, it may be important to picnickers to be able to drive to a picnic site.) Moderate impacts would change the desired experience appreciably, (i.e., changes one or more critical characteristics, or appreciably reduces/increases number of participants). Major impacts would eliminate or greatly enhance multiple critical characteristics or greatly reduce/increase participation.

Type of Impact. Impacts were evaluated in terms of whether they would be beneficial or adverse to visitor experience. Beneficial impacts would enhance visitor participation, quality of visitor experience, and service level. Adverse impacts would be effects that reduce visitor participation, quality of visitor experience, and service level.

For purposes of this analysis, an alternative is assumed to have an impact (adverse or beneficial) on park operations and facilities if it would:

• Result in direct changes to park operations, facilities, or staffing requirements or policies associated with park operations.
  
• Cause indirect effects on park operations, facilities, or staffing, such as effects on utility and roadway infrastructure, flooding, and impacts on provision of utilities, especially potable water and sewer services.

Duration of Impact. Short-term impacts would last only until all action items are completed. Long-term impacts would have a permanent effect on operations.

Intensity of Impact. With negligible impacts, there would not be a measurable difference in staffing compared to existing requirements. With minor impacts, measurable additions or reductions in staffing would be less than 15% of existing requirements. With moderate impacts, additions or reductions in staffing would be between 15% and 30% of existing requirements. With major impacts, additions or reductions in staffing would exceed 30% of existing requirements.

Type of Impact. Adverse impacts represent an increase in staffing requirements. Beneficial impacts represent a decrease in staffing requirements.

Yosemite National Park offers a broad spectrum of recreational opportunities. In addition, every visitor to Yosemite brings unique expectations, and thus each has a unique experience. The environmental assessment identifies, where possible, how the opportunity for recreation would change as a result of the Lower Yosemite Fall Project.

Duration of Impact. A short-term impact on visitor experiences would be temporary in duration and result from construction, restoration, or demolition activities. A long-term impact would have a permanent effect on the visitor experience.

Intensity of Impact. The intensity of impacts are defined as negligible, minor, moderate, and major. Negligible impacts would result in little noticeable change in recreational opportunities. Minor impacts would result in changes in desired recreational opportunities but without appreciably limiting or enhancing critical characteristics. (Critical characteristics are those elements of a recreational activity that are most important to those who pursue it; for example, it may be important to picnickers to be able to drive to a picnic site.) Moderate impacts would change the desired recreational opportunity appreciably (i.e., changes one or more critical characteristics, or appreciably reduces/increases number of participants). Major impacts would eliminate or greatly enhance multiple critical characteristics or greatly reduce/increase participation.

Size of user groups was defined based on a percentage of visitors who participate in a recreational activity in Yosemite Valley:

• Small; less than 1% of visitors, unless Yosemite Valley is a principal destination for this activity that cannot be replaced at other destinations, which moves user group to moderate.
  
• Moderate; 1% to 5% of visitors
  
• Moderately large; 6% to 19% of visitors
  
• Large; 20% to 49% of visitors
  
• Majority; 50% to 74% of visitors
  
• Most; 75% or more of visitors to Yosemite Valley.

Type of Impact. Impacts were evaluated in terms of whether they would be beneficial or adverse to recreation. Beneficial impacts would enhance recreational participation, quality or recreational opportunity. Adverse impacts would be effects that reduce recreational participation, quality of recreational opportunity, and service level.

To evaluate the changes in traffic volumes that would be generated by additional internal bus circulation, internal bus circulation volumes were compared qualitatively with traffic volumes under the No Action Alternative in the Yosemite Valley Plan (see Vol. Ib, pages 4.0-39 and 4.0-40). Internal bus circulation volumes were also compared to the level of service analysis for roadway segments and intersections considered in the Yosemite Valley Plan (see Vol. Ib, page 4.0-41).

Duration of Impact. Short-term impacts would last less than 5 years and would be created during the implementation phase of the alternative actions. A long-term impact would be a permanent change in visitor circulation following the implementation of an action.

Intensity of Impact. The range of impact intensities for bus volumes on Valley roadways is listed below:

• With a negligible impact, there would be no measurable or perceptible change in the number of bus trips or bus vehicle miles traveled on Valley roadways.
  
• With a minor impact, the change in the number of bus trips or bus vehicle miles traveled on Valley roads would be less than 25%.
  
• With a moderate impact, the change in the number of bus trips or bus vehicle miles traveled on Valley roads would be between 26% and 75%.
  
• With a major impact, the change in the number of bus trip or bus vehicles miles traveled on Valley roads would be greater than 75%.

These ranges are higher than the ranges of impact intensity defined for all vehicle miles of travel.

Type of Impact. Changes in the number of bus trips or bus vehicle miles traveled cannot be characterized as beneficial or adverse from a transportation perspective.

Gasoline and diesel are the primary fuels consumed by automobiles, trucks, and buses used in the Yosemite Valley. A California Air Resources Board model (called BURDEN) was used to estimate motor fuel consumption associated with proposed plans, employee commuting patterns, and utilization of National Park Service and concessioner vehicles that operate in the Valley. Annual fuel consumption for heavy trucks, urban buses, and shuttle buses was derived from vehicle-miles-traveled estimates and typical fuel economy values for these vehicle types.

Duration of Impact. The duration of the impact considers whether the impact would occur in the short term or long term. Generally, short-term impacts are temporary in nature, whereas long-term impacts would have a continuing effect on energy consumption. For this analysis, vehicle emissions were quantified for the 15-year (2000-2015) time period and are assumed to continue beyond 2015.

Intensity of Impact. The intensity of an impact was assigned based on whether the impact is judged to be negligible, minor, moderate, or major relative to Alternative 1. For this analysis, impacts that would increase or decrease energy consumption by 5% or less annually would be negligible; by 5% to 20% annually would be minor; by 21% to 50% annually would be moderate; and by more than 50% annually would be major.

Type of Impact. Impacts were considered to be either beneficial or adverse with respect to energy consumption. Beneficial energy impacts would reduce energy consumption, whereas adverse impacts would increase energy consumption.

A cumulative impact is described in regulations developed by the Council on Environmental Quality, Regulation 1508. 7, as follows:

A "cumulative impact" is the impact on the environment which results from the incremental impact of the action when added to other past, present, and reasonably foreseeable future actions regardless of what agency (Federal or non-Federal) or person undertakes such other actions. Cumulative impacts can result from individually minor but collectively significant actions taking place over a period of time.

For the purpose of this environmental assessment, a list of projects within Yosemite Valley was identified so that potential cumulative impacts from the Lower Yosemite Fall Project could be evaluated in the context of these other projects. Appendix C contains the list of cumulative projects included in the cumulative impact analysis. The other Yosemite Valley projects identified included past actions, as well as any planning or development activity currently being implemented or planned for implementation in the reasonably foreseeable future.

These cumulative actions are evaluated in the impact analysis in conjunction with potential impacts of each proposed project alternative to evaluate whether there may be additive effects on a particular natural, cultural, or social resource. Because most of the other projects included in the cumulative analysis are in the early planning stages, the evaluation of cumulative impacts was based on a general description of each project considered.

Pursuant to the 1916 Organic Act, the National Park Service has a management responsibility "to conserve the scenery and the natural and historic objects and the wildlife therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations." Therefore, the National Park Service cannot take an action that would "impair" park resources. The National Park Service Management Policies (NPS 2001a) provides guidance on addressing impairment.

Impairment is an impact that, in the professional judgment of the responsible National Park Service manager, would harm the integrity of park resources or values, including opportunities that otherwise would be present for the enjoyment of those resources or values. An impact would be less likely to constitute an impairment to the extent that it is an unavoidable result from an action necessary to preserve or restore the integrity of park resources or values (NPS 2001a). An impact would be more likely to constitute impairment to the extent that it affects a resource or value whose conservation is:

• Necessary to fulfill specific purposes identified in the establishing legislation or proclamation of the park.
  
• Key to the natural or cultural integrity of the park or to opportunities for enjoyment of the park.
  
• Identified as a goal in the park’s General Management Plan or other relevant National Park Service planning documents.

Impairment of park resources was evaluated on the basis of the type and intensity of impact and in terms of the types of resources affected. In general, beneficial impacts do not constitute impairment. With respect to the intensity of impacts, negligible and minor adverse impacts are not of sufficient magnitude to constitute impairment. Moderate and major adverse impacts may constitute impairment, but do not automatically do so. Rather, these impacts must be analyzed with respect to the three bulleted criteria above.

The National Park Service Director’s Order #12 (Conservation Planning, Environmental Impact Analysis, and Decision-Making) requires that impairment be addressed in all environmental assessments and draft and final environmental impact statements, as well as in the decision documents (for example, Finding of No Significant Impact or Record of Decision).

Analysis of Environmental Consequences

The analysis section includes direct and indirect effects for each resource topic, an analysis of cumulative impacts, and impairment of park resources for all alternatives.

• Restroom Location. The existing restroom would continue to be located in its current location, which is not within or near any existing jurisdictional or Cowardin wetlands.
  
• Parking Area. The existing parking area would continue in its current location, which is not near any existing jurisdictional or Cowardin wetlands.
  
• Shuttle Bus Stop. The shuttle bus stop would continue in its current location, which is not located near any existing jurisdictional or Cowardin wetlands. A new shuttle bus stop would not be provided.
  
• Tour Bus Unloading, Loading, and Parking. The tour buses that park in the existing parking area would continue to not impact existing jurisdictional or Cowardin wetlands.
  
• Trail Alignment. Under Alternative 1, human use and trampling in wetland areas where trails are not well defined may continue to degrade existing jurisdictional or Cowardin wetlands in the Lower Yosemite Fall area.
  
• Rehabilitation of Trails. Under Alternative 1, human use and trampling in wetland areas where trails are not well defined may continue to degrade existing jurisdictional or Cowardin wetlands in the Lower Yosemite Fall area.
  
• Rehabilitation, Relocation, and Installation of Bridges. All bridges in the Lower Yosemite Fall area have abutments within creek channels classified as Cowardin wetlands. In addition, the abutments of Bridge #5 are located in a jurisdictional wetland. Hydrologic flows that support wetlands would continue to be diverted and constricted by these bridge abutments.
  
• View Corridor Maintenance. No trees or vegetation would be removed to maintain view corridors; therefore, no jurisdictional or Cowardin wetlands would be affected.
  
• Removal of Human-Built Rock-Rubble Pile. The rock-rubble pile would continue in its present location; it would not affect identified jurisdictional or Cowardin wetlands.

Overall, there would be a long-term, minor, adverse impact on wetlands under Alternative 1 resulting from human use and trampling in areas where trails are not well defined as well as from bridge abutments (located within creek channels) that could alter hydrologic flows that support wetlands.

Throughout Yosemite Valley, a net gain of approximately 118 acres of wetland would take place under the adopted Yosemite Valley Plan. About 141 acres of wetlands would be restored, 12 acres of new development in wetlands would take place, and 11 acres of redevelopment in degraded wetlands could take place. Overall, regardless of the continuing impacts to wetlands in the local setting, there would be a long-term, major, beneficial impact on the size of wetlands in Yosemite Valley.

Wetland impacts resulting from Alternative 1 would not be of sufficient magnitude to constitute impairment.

• Restroom Relocation. Long-term, negligible, beneficial impact. The new restroom would be located in the southeast portion of the area currently occupied by the parking lot. This area is not within or near any identified jurisdictional or Cowardin wetlands.
  
• Parking Area Removal and Establishment of Seating/Picnic Area. Long-term, negligible, beneficial impact. Project activities would not occur within or near any identified jurisdictional or Cowardin wetlands.
  
• New Shuttle Bus Stop. Long-term, negligible, beneficial impact. The new shuttle bus stop would not be placed within or near any identified jurisdictional or Cowardin wetlands.
  
• Interim Tour Bus Unloading, Loading, and Parking. Short-term, negligible, beneficial impact. Tour bus unloading, loading, and parking would not occur within or near any identified jurisdictional or Cowardin wetlands.
  
• Trail Alignment. Long-term, negligible, beneficial impact. None of the trail alignments would occur within any identified jurisdictional or Cowardin wetlands.
  
• Rehabilitation of Trails. Long-term, minor, beneficial impact. Trail rehabilitation activities would not occur within any identified Cowardin wetlands. These impacts would be slightly detectable and localized throughout the local setting.
  
• Rehabilitation, Relocation, and Installation of Bridges. Long-term, minor, beneficial impact. Proposed reconstruction of Bridge #5 would completely span the identified jurisdictional wetland in this area. Negligible amounts of fill would be placed within the Cowardin wetlands at Bridge #3 and Bridge #6 due to the placement of bridge piers. All bridge abutments would be removed from the stream channel to upland areas. Overall, hydrologic flows under the rehabilitated bridges would improve wetland conditions, resulting in local, long-term, minor, beneficial impacts. The two piers at the Yosemite Falls Bridge would be replaced in the same location and result in no new wetland impact. Under Alternative 2, the hydrologic flows and wetland conditions would be improved.
  
• View Corridor Maintenance. Long-term, negligible, adverse impact. Selected vegetation would be removed in view corridors; however, wetland plant species would be avoided to the extent possible.
  
• Removal of Human-Built Rock-Rubble Pile. Long-term, negligible, beneficial impact. The rock-rubble pile removal would be preceded by studies on wetlands, hydrology, and cultural resources, and appropriate public health and safety measures would be applied.

Overall, there would be a long-term, minor, beneficial impact on wetlands due to the removal of bridge abutments from creek channels.

Cumulative impacts on wetlands are described previously in this chapter for Alternative 1. Alternative 2 would result in long-term, minor, beneficial impacts to wetlands, which in combination with cumulative actions, would contribute to a long-term, major, beneficial cumulative impact on the size and condition of wetlands in the Yosemite Valley.

Wetland impacts resulting from Alternative 2 would not be of sufficient magnitude to constitute impairment.

• Restroom Relocation. Long-term, negligible, beneficial impact. The new restroom would be located in an area adjacent to the trail leading from Northside Drive to Bridge #6. This area is not within or near any identified Cowardin or jurisdictional wetlands.
  
• Parking Area Removal and Establishment of an Informal Seating Area. Long-term, negligible, beneficial impact. Project activities would not occur within or near any identified Cowardin or jurisdictional wetlands.
  
• New Shuttle Bus Stop. Long-term, negligible, beneficial impact. The new shuttle bus stop would not be placed within or near any identified Cowardin wetlands.
  
• Interim Tour Bus Unloading, Loading, and Parking. Short-term, negligible, beneficial impact. Tour bus unloading, loading, and parking would not occur within or near any identified Cowardin or jurisdictional wetlands.
  
• Trail Alignment. Long-term, negligible, beneficial impact. None of the trail alignments would occur within any identified Cowardin or jurisdictional wetlands.
  
• Rehabilitation of Trails. Long-term, minor, beneficial impact. Trail rehabilitation activities would not occur within any identified Cowardin or jurisdictional wetlands. These impacts would be slightly detectable and localized throughout the local setting.
  
• Rehabilitation, Relocation, and Installation of Bridges. Long-term, minor, beneficial impact. Proposed reconstruction of Bridge #5 would completely span the identified jurisdictional wetland in this area. Negligible amounts of fill would be placed within the Cowardin wetlands at Bridge #3 and Bridge #6 due to the placement of bridge piers. All bridge abutments would be removed from the stream channel to upland areas. Overall, hydrologic flows under the rehabilitated bridges would improve wetlands conditions. The two piers at the Yosemite Falls Bridge would be replaced in the same location, and result in no new wetlands impacts.
  
• View Corridor Maintenance. Long-term, negligible, adverse impact. Selected vegetation would be removed in view corridors; however, wetland plant species would be avoided to the extent possible.
  
• Removal of Human-Built Rock-Rubble Pile. Long-term, negligible, beneficial impact. The rock-rubble pile would be removed without the benefit of studies on wetlands, hydrology, and cultural resources being performed and appropriate public health and safety measures being applied.

Overall, there would be a long-term, minor, beneficial impact on wetlands resulting from the removal of bridge abutments from creek channels.

Additional cumulative impacts on wetlands have been described previously in this chapter for Alternative 1. In combination with Alternative 3, there would be a long-term, major, beneficial cumulative impact on the size and condition of wetlands in Yosemite Valley.

Wetland impacts resulting from Alternative 3 would not be of sufficient magnitude to constitute impairment.

• Restroom Location. Long-term, minor, adverse impact. The restroom would continue to be located in its current location; the facility is classified as a Miscellaneous Structure and is located within the rockfall shadow zone. (See the Final Yosemite Valley Plan/SEIS, Vol. II, Appendix C, figure C-1 for occupancy categories.) There would be no change in soil erosion at the location of the restroom.
  
• Parking Area. Long-term, minor, adverse impact. The existing parking area would continue in its current location. The facility is classified as "miscellaneous" and is located within the rockfall shadow zone. There would be no change in soil erosion in the area.
  
• Shuttle Bus Stop. There would be no change in rockfall hazards and soil erosion in the area as the result of current shuttle bus stop operations for the Lower Yosemite Fall area.
  
• Tour Bus Unloading, Loading, and Parking. Long-term, minor, adverse impact. Bus loading, unloading, and parking would continue within the rockfall shadow zone. There would be no change in rockfall hazards. There would be no soil erosion as a result of current tour bus parking.
  
• Trail Alignment. Under Alternative 1, trails would continue in their current alignments. This current alignment may encourage off-trail use by visitors wanting to take more direct routes or shortcuts to access viewing areas. As a result, soils may continue to be disturbed and soil erosion may continue in off-trail areas most heavily used by visitors. There would be no change in rockfall hazards.
  
• Rehabilitation of Trails. Under Alternative 1, trails would continue in their current condition. Where trails are deteriorated or undefined, off-trail use may result. Visitors may continue to wander away from trails to access viewing areas. As a result, soils may be disturbed and soil erosion may continue in off-trail areas most heavily used by visitors. There would be no change in rockfall hazards.
• Rehabilitation, Relocation, and Installation of Bridges. Under Alternative 1, all bridges in the area would continue in their current condition. Without the rehabilitation, relocation, and installation of certain bridges, human use and trampling of off-trail areas may continue. Stream bank soil erosion may continue in areas where bridges are not accessible for visitors to cross creek channels (e.g., Bridge #6). There would be no change in rockfall hazards.
  
• View Corridor Maintenance. No trees or vegetation would be removed to maintain view corridors; therefore, no soils would be affected. There would be no change in rockfall hazards.
  
• Removal of Human-Built Rock-Rubble Pile. Because the rock-rubble pile would not be removed, soils would not be affected. There would be no change in rockfall hazards.

Overall, under Alternative 1 there would be a long-term, negligible, adverse impact on soils from off-trail use that could increase erosion. There would be a long-term, negligible, adverse impact on geology or geologic hazards due to retention of the restroom and the parking area within the rockfall shadow zone.

Past facility development has occurred in areas that are susceptible to damage from geohazards (rockfalls and seismic events) and has contributed to the overall degradation of soil resources in the park. These facilities include lodging, visitor centers, campgrounds, and bridges, with associated roads and parking lots. In addition, facilities required to support park infrastructure, including employee housing, utility facilities, maintenance yards, and supply storage areas, have been developed throughout the Valley.

Rockfall hazards would be reduced through projects that relocate people and facilities away from rockfall hazard zones, such as removal of units at Housekeeping Camp and Curry Village located within the talus slope zone, as identified in the Yosemite Valley Plan. However, other projects could expose additional visitors to the risk of rockfalls, such as the Trail Reconstruction from Happy Isles to Vernal Fall and Happy Isles Site Improvements. Most of the Lower Yosemite Fall area is located in the rockfall shadow zone. The Yosemite Falls Bridge is located in the talus slope zone. In addition, earthquakes are unavoidable and unpredictable, and represent a potentially long-term, adverse impact to public health and safety. Past, present, and reasonably foreseeable future actions would result in local, long-term, minor, beneficial cumulative impacts to public health and safety from geologic hazards due to an overall reduction in the density of people and facilities in the talus slope zone.

Certain development projects could result in increased degradation of soil resources, such as expansion of campgrounds and construction of lodging and employee housing in Yosemite Valley, as identified in the Yosemite Valley Plan. However, other projects related to habitat restoration, such as removal of roads through Stoneman and Ahwahnee Meadows, and the Merced River at Eagle Creek Ecological Restoration (Yosemite Valley), would have long-term, beneficial effects on soils. Although these types of projects may have slight site-specific, short-term, adverse effects (e.g., potential construction erosion and soil loss), an objective of these projects is to restore and manage natural resources and reduce soil degradation. For example, full implementation of the Yosemite Valley Plan would restore approximately 177 acres of soil, of which approximately 136 acres would be high-value resource soils in Yosemite Valley. The cumulative projects would result in local, long-term, minor, beneficial cumulative impacts to soil resources.

Alternative 1 and the cumulative projects would result in a local, long-term, minor, beneficial impact to public safety in Yosemite Valley due to the overall reduction in the density of facilities in the talus slope and rockfall shadow zones. The local, long-term, minor, beneficial impacts to soil resources under the cumulative projects would be somewhat diminished by the potential soil erosion and bank destabilization under Alternative 1, resulting in a net local, long-term, negligible, beneficial impact to soil resources.

Geology, geologic hazards, and soil impacts resulting from Alternative 1 would not be of sufficient magnitude to constitute impairment.

• Restroom Relocation. Long-term, negligible, beneficial impact. Soils-specific mitigation measures that would be used during restroom demolition and construction of the new restroom would largely offset adverse impacts to soils from these activities. In addition, the new location of the restroom would be outside the rockfall shadow zone.
  
• Parking Area Removal and Establishment of Seating/Picnic Area. Long-term, minor, adverse impact. Soils-specific mitigation measures that would be used during the removal of the parking area and the installation of seating structures would prevent adverse impacts to soils from these activities. There would be a minor risk from geologic hazards (rockfall) as a result of activities under Alternative 2 because the picnic area and seating area would be partly within the rockfall shadow zone.
  
• New Shuttle Bus Stop. Long-term, negligible, beneficial impact. Establishment of the new shuttle bus stop would not require soil disturbance because it would be located in a previously paved area. In addition, there would be no increased risk from geologic hazards (rockfall) as a result of activities under Alternative 2.
  
• Interim Tour Bus Unloading, Loading, and Parking. Short-term, negligible, beneficial impact. Establishment of the interim tour bus unloading, loading, and parking area would not result in soil disturbance because it would be located in a previously paved area. There would be a negligible, minor risk from geologic hazards (rockfall) as a result of activities under Alternative 2 because the interim bus loading and unloading and parking would not place facilities inside the rockfall shadow zone.
  
• Trail Alignment. Long-term, minor, beneficial impact. The trail alignments to be constructed under Alternative 2 would allow visitors better access to viewing areas while staying on designated paths. As a result, disturbance and erosion of soils in off-trail areas would be reduced. Soils-specific mitigation measures that would be used for trail alignment would prevent adverse impacts to soils from this activity. In addition, there would be no increased risk from geologic hazards (rockfall) as a result of activities under Alternative 2.
  
• Rehabilitation of Trails. Long-term, minor, beneficial impact. Under Alternative 2, trails would be paved and widened to allow easier access to viewing areas. With better-defined trails, human use and trampling of off-trail areas would be reduced, thereby reducing soil disturbance and erosion. Construction and rehabilitation of trails could bring visitors in proximity to contaminated soils identified at the waste accumulation area within the vicinity of Bridge #7 (to be constructed). Soils-specific and construction-specific mitigation measures that would be used for trail rehabilitation would prevent adverse impacts to soils and exposure to contaminated soils during this activity. In addition, there would be no increased risk from geologic hazards (rockfall and seismic shaking) as a result of activities under Alternative 2.
  
• Rehabilitation, Relocation, and Installation of Bridges. Long-term, minor, beneficial impact. Rehabilitation, relocation, and installation of the bridges would help to discourage human use and trampling of off-trail areas. Stream bank soil erosion would be reduced because all bridges in the area would be accessible for visitors to cross creek channels. The construction of Bridge #7 could bring visitors in proximity to contaminated soils identified at the waste accumulation area. The soils-specific and construction-specific mitigation measures that would be used for bridge rehabilitation and construction would prevent adverse impacts to soils and exposure to contaminated soils from these activities. There would be no change in rockfall hazards under Alternative 2.
  
• View Corridor Maintenance. Short-term, negligible, adverse impact. Selected vegetation would be removed in view corridors. The removal of trees and plants for vista maintenance would represent a slight disturbance to soils in the area; however, these impacts would be negligible. There would be no change in rockfall hazards under Alternative 2.
  
• Removal of Human-Built Rock-Rubble Pile. Short-term, negligible, beneficial impact. The rock-rubble pile removal would be preceded by studies of hydrology, cultural resources, and wetlands, and appropriate public health and safety measures would be applied. There would be a negligible impact to geology, geohazards, or soils.

Overall, there would be a long-term, minor, beneficial impact on soils due to better defined trails that would reduce heavy use in off-trail areas under Alternative 2. There would be a long-term, minor, adverse impact on geology or geologic hazards due to placement of the picnic area and seating area partially within the rockfall shadow zone.

The impacts of cumulative actions are described under Alternative 1. In combination with Alternative 2, there would be no change from Alternative 1 in the cumulative effects on geology, geologic hazards, and soils within the park. There would be a local, long-term, minor, beneficial cumulative impact to public safety in Yosemite Valley due to the overall reduction in the density of facilities in the talus slope and rockfall shadow zones. There would be a local, long-term, negligible, beneficial cumulative impact to soil resources.

Geology, geologic hazards, and soils impacts resulting from Alternative 2 would not be of sufficient magnitude to constitute impairment.

• Restroom Relocation. Long-term, negligible, beneficial impact. Soils-specific mitigation measures that would be used during restroom demolition and construction of the new restroom would prevent adverse impacts to soils from these activities. In addition, the new location of the restroom would be outside the rockfall shadow zone.
  
• Parking Area Removal and Establishment of an Informal Seating Area. Long-term, minor, adverse impact. Soils-specific mitigation measures that would be used during the removal of the parking area and the installation of seating structures would largely offset adverse impacts to soils from these activities. There would be a minor risk from geologic hazards (rockfall) as a result of activities under Alternative 3 because the seating area would be partially within the rockfall shadow zone.
  
• New Shuttle Bus Stop. Long-term, negligible, beneficial impact. Establishment of the new shuttle bus stop would not require soil disturbance because it would be located in a previously paved area. In addition, there would be no increased risk from geologic hazards (rockfall) as a result of activities under Alternative 3.
  
• Interim Tour Bus Unloading, Loading, and Parking. Short-term, negligible, beneficial impact. Establishment of the interim tour bus unloading, loading, and parking area would not result in soil disturbance because it would be located in a previously paved area. There would be a negligible risk from geologic hazards (rockfall) as a result of activities under Alternative 3, because a portion of the loading and unloading and the interim bus parking would not place structures inside the rockfall shadow zone.
  
• Trail Alignment. Long-term, minor, beneficial impact. The trail alignments to be constructed under Alternative 3 would allow visitors better access to viewing areas while staying on designated paths. As a result, disturbance and erosion of soils in off-trail areas would be reduced. Soils-specific mitigation measures that would be used for trail alignment would prevent adverse impacts to soils from this activity. In addition, there would be no increased risk from geologic hazards (rockfall) as a result of activities under Alternative 3.
  
• Rehabilitation of Trails. Long-term, minor, beneficial impact. Under Alternative 3, trails would be paved and widened to allow easier access to viewing areas. With better-defined trails, human use and trampling of off-trail areas would be reduced, thereby reducing soil disturbance and erosion. Construction and rehabilitation of trails could bring visitors in proximity to contaminated soils identified at the waste accumulation area within the vicinity of Bridge #7 (to be constructed). Soils-specific and construction-specific mitigation measures that would be used for trail rehabilitation would prevent adverse impacts to soils and exposure to contaminated soils during this activity. In addition, there would be no increased risk from geologic hazards (rockfall) as a result of activities under Alternative 3.
  
• Rehabilitation, Relocation, and Installation of Bridges. Long-term, minor, beneficial impact. Rehabilitation, relocation, and installation of the bridges would help to discourage human use and trampling of off-trail areas. Stream bank soil erosion would be reduced because all bridges in the area would be accessible for visitors to cross creek channels. The construction of Bridge #7 could bring visitors in proximity to contaminated soils identified at the waste accumulation area. The soils-specific and construction-specific mitigation measures that would be used for bridge rehabilitation and construction would prevent adverse impacts to soils, and exposure to contaminated soils from these activities. There would be no change in rockfall hazards or seismic shaking under Alternative 3.
  
• View Corridor Maintenance. Short-term, negligible, adverse impact. Selected vegetation would be removed in view corridors. The removal of trees and plants for vista maintenance would represent a slight disturbance to soils in the area; however, these impacts would be negligible. There would be no change in rockfall hazards under Alternative 3.
  
• Removal of Human-Built Rock-Rubble Pile. Short-term, negligible, beneficial impact. The rock-rubble pile would be removed without the benefit of studies on hydrology, cultural resources, and wetlands being performed and appropriate public health and safety protection measures being applied. There would be a negligible impact to geology, geohazards, or soils.

Overall, there would be a long-term, minor, beneficial impact on soils due to more well-defined trails that would reduce heavy use in off-trail areas under Alternative 3. There would be a long-term, minor, adverse impact on geology or geologic hazards due to placement of the seating area partially within the rockfall shadow zone.

The impacts of cumulative actions are described under Alternative 1. In combination with Alternative 3, there would be no change from Alternative 1 in the cumulative effects on geology, geologic hazards, and soils within the park. There would be a local, long-term, minor beneficial impact to public safety in Yosemite Valley due to the overall reduction in the density of facilities in the talus slope and rockfall shadow zones. There would be a local, long-term, negligible, beneficial impact to soil resources.

Geology, geologic hazards, and soil impacts resulting from Alternative 3 would not be of sufficient magnitude to constitute impairment.

• Restroom Location. The existing restroom would continue to be located in its current location, which is not within or near any creek channels; therefore, water quality would not be affected.
  
• Parking Area. Long-term, minor, adverse impact. The existing parking area would continue to represent a potential non-point source of pollution with the heavy use and concentrated presence of vehicles in the area. (Non-point source pollution occurs when water runs over land or through the ground, picks up pollutants, and deposits them in surface waters or introduces them into groundwater.) Surface runoff from the parking area could adversely affect the water quality of nearby creeks.
  
• Shuttle Bus Stop. Long-term, minor, adverse impact. Shuttle buses would continue to stop at the northeast corner of the existing parking area. Surface runoff from the parking area would continue to (potentially) adversely affect the water quality of Yosemite Creek.
  
• Tour Bus Unloading, Loading, and Parking. Long-term, minor, adverse impact. Tour buses would continue to park within the existing parking area. Surface runoff from the parking area would continue to (potentially) adversely affect the water quality of Yosemite Creek.
  
• Trail Alignment. Long-term, minor, adverse impact. Under Alternative 1, current trail alignments would continue to encourage human use and trampling in creek channels. This activity would continue to degrade hydrologic processes and water quality of creeks in the area.
  
• Rehabilitation of Trails. Long-term, minor, adverse impact. Under Alternative 1, human use and trampling in creek areas as the result of poorly defined trails may continue to degrade hydrologic processes and water quality of creeks.
  
• Rehabilitation, Relocation, and Installation of Bridges. Long-term, minor, adverse impact. Under Alternative 1, all bridges in the Lower Yosemite Fall area would continue to constrict and alter water flows. This could contribute to accelerated erosion on adjacent riverbanks associated with constricted flows.
  
• View Corridor Maintenance. No trees or vegetation would be removed to maintain view corridors; therefore, no creeks would be affected.
  
• Removal of Human-Built Rock-Rubble Pile. Long-term, negligible, adverse impact. The rock-rubble pile removal would be preceded by studies of hydrology, cultural resources, and wetlands, and appropriate public health and safety measures would be applied.

Overall, there would be a long-term, minor, adverse impact on hydrology and water quality under Alternative 1 due to surface runoff from the parking lot, which could introduce pollutants into nearby creeks.

The Merced River has been previously affected by a variety of projects that have introduced obstructions into the river channel, modified the floodplain, and adversely affected hydrology. Examples of actions that have had adverse effects on the hydrologic processes of the Merced River include lowering of the El Captain moraine; placement of riprap; removal of large woody debris; and construction of bridges, dikes, flood walls, impoundments, dams, and buildings. Conversely, actions such as riverbank restoration projects, removal of impoundments and bridges, and limiting visitor use to particular areas help restore the natural river flow and reduce bank erosion.

Reasonably foreseeable future projects that would have beneficial impacts on hydrologic processes and water quality include such restoration actions as those presented in the Yosemite Valley Plan. Elements of the Yosemite Valley Plan include removal of Sugar Pine Bridge, which constrains flows of the Merced River; restoration to natural conditions of campgrounds located within the floodplain; and removal of facilities from the 100-year floodplain.

Alternatively, adverse impacts could occur by implementing projects called for in the Yosemite Valley Plan, including construction of additional lodging, campsites, and a visitor transit center in the Valley.

Overall, implementation of the Yosemite Valley Plan would have a beneficial effect on river hydrologic processes and water quality.

The Merced Wild and Scenic River Comprehensive Management Plan (Merced River Plan) (NPS 2001b) protects river-related resources through the application of seven management elements. These elements are the River Protection Overlay, management zoning, protection and enhancement of Outstandingly Remarkable Values, Section 7 determination process under the Wild and Scenic Rivers Act, classifications, boundary delineation, and implementation of a Visitor Experience Resource Protection framework (refer to the Merced River Plan for descriptions of these management elements).

Other future projects include the Happy Isles Bridge Replacement Project, Repair of Flood Damaged Trails at Happy Isles, Merced River at Eagle Creek Ecological Restoration (Yosemite Valley), and the Replacement/Rehabilitation of the Yosemite Valley Main Sewer Line. Cumulatively, these projects are anticipated to have beneficial impacts on hydrologic processes and water quality of the Merced River.

While some of the past, present, and reasonably foreseeable future projects along the Merced River in Yosemite Valley would ultimately remove constrictions to streamflows, enhance water quality, rehabilitate eroded streambanks, and reduce degradation of stream characteristics in the Merced River, others would result in adverse water quality impacts and bank erosion. Thus, the cumulative projects would result in a local, long-term, minor, beneficial impact to hydrologic processes and water quality.

The past, present, and future projects in Yosemite Valley, considered cumulatively with Alternative 1, would have a local, long-term, minor beneficial effect on hydrologic processes and water quality in Yosemite Valley.

Hydrology and water quality impacts resulting from Alternative 1 would not be of sufficient magnitude to constitute impairment.

• Restroom Relocation. Long-term, negligible, beneficial impact. Hydrology/water quality-specific mitigation measures (including surface-runoff control) that would be used during Alternative 2 restroom demolition and construction would substantially minimize adverse impacts to Yosemite Creek during these activities. Also, a portion of the area would be revegetated, thereby restoring surface hydrology and improving water quality in the long term.
  
• Parking Area Removal and Establishment of Seating/Picnic Area. Long-term, minor, beneficial impact. The parking area removal would remove a non-point source of pollution from creeks in the area. The non-point pollution source would be moved to other parking areas where water quality protection measures meet regulations specified in the Clean Water Act. (Note: More detailed mitigation measures are presented in Chapter 2, Description of Proposed Action and Alternatives.) Hydrology/water quality-specific mitigation measures under Alternative 2 (including surface-runoff control) that would be used during parking lot removal and seating/picnic area construction would prevent adverse impacts to creeks during these activities.
  
• New Shuttle Bus Stop. Long-term, negligible, beneficial impact. Under Alternative 2, the new shuttle bus stop would be along Northside Drive at a location that is already paved, and where vehicles already stop periodically. Surface runoff would not be affected by any additional pollutant types or amount from the new shuttle bus stop beyond that normally associated with runoff from paved roadways.
  
• Interim Tour Bus Unloading, Loading, and Parking. Short-term, negligible, adverse impact. Under Alternative 2, the interim tour bus unloading and loading zone would be along Northside Drive at a location that is already paved, and where vehicles already stop periodically. Surface runoff could be marginally affected by additional pollutants from tour buses beyond that normally associated with runoff from paved roadways.
  
• Trail Alignment. Long-term, minor, beneficial impact. Under Alternative 2, trail alignments would provide visitors with more defined access to viewing areas, thereby discouraging the trampling of creek channels. Overall, this would benefit the hydrologic processes and water quality of creeks in the area. Hydrology/water quality-specific mitigation measures (including surface-runoff control) that would be used during trail alignment would prevent adverse impacts to creeks during these activities.
  
• Rehabilitation of Trails. Long-term, minor, beneficial impact. Under Alternative 2, trail rehabilitation would provide visitors with more defined access to viewing areas, thereby discouraging the trampling of creek channels. Overall, this would benefit the hydrologic processes and water quality of creeks in the area. Hydrology/water quality-specific mitigation measures (including surface-runoff control) that would be used during trail rehabilitation would prevent adverse impacts to creeks from these activities.
  
• Rehabilitation, Relocation, and Installation of Bridges. Long-term, moderate, beneficial impact. Under Alternative 2, all bridges would be rehabilitated to accommodate larger flows. Bridge abutments would be moved out of creek channels and located further up on the banks. This would enlarge the opening under each bridge, remove the current constricting abutments, reduce bank erosion associated with the constricted openings, and accommodate more water under the bridge. The piers at Bridges #3 and #6 would cause a slightly perceptible change to creek hydrology. Overall, the bridges would be designed to improve hydrology and accommodate minor shifts in the channel. There would be no change in hydrologic processes at the Yosemite Falls Bridge as a result of its rehabilitation. Hydrology/water quality-specific mitigation measures (including runoff control) that would be used for bridge rehabilitation, relocation, and installation would largely offset adverse impacts to water quality and hydrology from these activities.
  
• View Corridor Maintenance. Long-term, negligible, adverse impact. Selected vegetation would be removed in view corridors. The removal of trees and plants for maintenance of the Hutchings view corridor would have imperceptible effects to the creek hydrology. Vista maintenance would be conducted with appropriate mitigation measures to largely offset adverse impacts to hydrologic processes and water quality.
  
• Removal of Human-Built Rock-Rubble Pile. Long-term, minor, beneficial impact. The rock-rubble pile removal would be preceded by studies of hydrology, cultural resources, and wetlands, and appropriate public health and safety measures would be applied. The results of these studies would be used to maximize the potential for hydrologic restoration without adversely affecting public health and safety.

Overall, there would be a long-term, moderate, beneficial impact on hydrology and water quality under Alternative 2 due to the removal of the parking lot and removal of the bridge abutments from creek channels to accommodate hydrologic flows.

The cumulative impact analysis for hydrology and water quality in Alternative 2 is the same as described under Alternative 1 earlier in this chapter. The past, present, and future projects in Yosemite Valley, considered cumulatively with Alternative 2, would have a local, long-term, minor, beneficial impact on hydrologic processes and water quality in Yosemite Valley.

Hydrology and water quality impacts resulting from Alternative 2 would not be of sufficient magnitude to constitute impairment.

• Restroom Relocation. Long-term, negligible, beneficial impact. Hydrology/water quality-specific mitigation measures (including surface-runoff control) that would be used during restroom demolition and construction would substantially minimize adverse impacts to creeks during these activities. Also, a portion of the area would be revegetated, thereby restoring surface hydrology and improving water quality in the long term.
  
• Parking Area Removal and Establishment of an Informal Seating Area. Long-term, minor, beneficial impact. The parking area removal would remove a non-point source of pollution for creeks in the area. Hydrology/water quality-specific mitigation measures (including surface-runoff control) that would be used during parking lot removal and seating area construction (presented in detail in Chapter 2, Description of the Proposed Action and Alternatives) would prevent adverse impacts to creeks during these activities.
  
• New Shuttle Bus Stop. Long-term, negligible, beneficial impact. The new shuttle bus stop would be along Northside Drive at a location that is already paved, and where vehicles already stop periodically. Surface runoff would not be affected by any additional pollutant types or amount from the new shuttle stop beyond that normally associated with runoff from paved r